Sombra is here... kinda.
If you are attending Blizzcon you can play with Sombra right now. If you are a pleb like me you'll need to wait until next week to put your hands on her.
My opinon on her kit is she look powerful. Invisibilty and teleport on the same character? Mass disable?
But the point isn't about how good she is but instead of if she is good enough to replace the current Attack characters.
Since ranked pray to the 2-2-2 gods she'll take the spots of all the Meis / Reapers / McCrees / Tracers / Genjis out there.
My humble opinion is she is probably stronger them all those characters because if you combo her ulti with pretty much ANY ultimate in the game, it's a teamwipe.
On the other side, you need to combo 2 ultis, and on the wild world of solo queue this is harder than it looks otherwise Zarya would rule the world.
Plus, if you played with a spy on your team in TF2, you know it's the kind of character which can fail hard and have minimal impact in the match.
In a nutshell, if you are very good, the combo of invisibility plus disable will wreck teams, but if you are not on the top of you game you'll be like one of those Genjis which dash into walls and die.